Various developments having been disclosed so far include, for example, a so-called direct type radiation imaging apparatus wherein an electric charge is generated by a detection element in response to the dosage of the radiation such as X-ray having been applied, and is converted into an electric signal, or a so called indirect type radiation imaging apparatus wherein, after the applied radiation has been converted into the electromagnetic wave of another wavelength such as visible light by a scintillator and others, an electric charge is generated by a photoelectric conversion element such as a photodiode in response to the energy of the electromagnetic wave having been converted and applied, and is converted into electric signals. In the present invention, both the detection element in the direct type radiation detection element and the detection element in the indirect type radiation detection element are collectively called a radiation detection element.
The radiographic imaging apparatus of this type has been known under the name of FPD (Flat Panel Detector). This apparatus has been formed integral with a support base (or Bucky's radiological device) (Patent Literature 1). The development in recent years includes a portable radiographic imaging apparatus wherein the radiation detection element and others are accommodated in a housing. This has been put into practical use (Patent Literatures 2 and 3).
Incidentally, in some of the aforementioned radiographic imaging apparatuses, particularly portable radiographic imaging apparatuses, information on the start and termination of irradiation is sent to the radiographic imaging apparatus from an irradiation apparatus or an external device such as a computer for managing the system. After application of radiation in the radiographic imaging apparatus in response thereto, the image data is read from each of the radiation detection elements.
However, the aforementioned structure requires an interface to be provided between the irradiation apparatus or computer and the radiographic imaging apparatus so that control is provided by the overall system including the irradiation apparatus and computer. This will result in a large and complicated structure wherein the radiographic imaging apparatus recognizes the start and termination of irradiation. Thus, it is desirable to work out a structure that permits the start and termination of irradiation to be identified by the radiographic imaging apparatus itself.
In this case, the radiographic imaging apparatus can be provided with a sensor or the like to identify the start and termination of the irradiation. However, this structure requires a space for installing a sensor inside the radiographic imaging apparatus, with the result that the apparatus is increased in size. Further, if a sensor is provided, the power for driving the sensor is required. Particularly, the portable radiographic imaging apparatus has a problem of the built-in battery being consumed.
A solution to this problem has been proposed (Patent Literature 4). To be more specific, means are provided to detect the current flowing through the bias line for applying a bias voltage to each of the radiation detection elements. There is an increase of current flowing through the bias line when an electric charge is generated inside the radiation detection elements by irradiation. Thus, the start and termination of the irradiation is identified by detecting this change in the current value. This structure ensures easy identification of the start and termination of irradiation and reduced power consumption by providing the existing wiring with a current detecting section.